The invention concerns a sheathing pipe for a steel rod.
Basically, one way of protecting concrete building structures from corrosion is through the high alkalinity of the concrete, which causes a passive, rust-resistant layer to form on the surface of a steel rod. But the corrosion damage to steel-concrete structures that has been found in recent years primarily involves traffic structures, like bridges, and the primary cause of the damage was the effect of road salt. In addition to salt, the passive layer on the surface of the steel can also be destroyed, for example, when the concrete reacts with carbon dioxide in the surrounding air and thus loses its alkalinity through calcification.
In order to protect the surface of steel suspension supports from the destruction of the protective passive layer described, such steel rods are surrounded with an insulating sheathing pipe, especially one made of plastic. In evaluating the structural status of structures provided with such sheathed suspension steel, however, the problem arises whether the sheathing is 100% effective in preserving the protective surface layer of the rod. The object of the invention is to make it possible to determine this with more certainty.